The attention of the world has been focused for weeks on a vast expanse of the treacherous Indian Ocean, transfixed by the strange and discomfiting human tragedy of flight MH370.

It's a moment at which all our ingenuity as a species collides with the immortal implacability of the elements; all the gadgets and connectivity in the world cannot appreciably moderate the task of finding a tiny so-called black box under seven kilometres of roiling, angry water, especially when you're not sure where to look.

About 3000 kilometres to the north-east, up at the very top of the ''V'' bitten out of South Australia by the Southern Ocean, another disappearance is baffling locals.

More than a hundred thousand cross-dressing, glow-in-the-dark creatures with remote-controlled skin and three hearts apiece have disappeared, and no one knows exactly why.

The area is Point Lowly, right up the top of Spencer Gulf, where in the shallow salty waters just offshore, every winter, the Australian giant cuttlefish come to mate.

The giant cuttlefish is the strangest creature alive. It is huge - up to a metre long - with eight tentacles bunched up the front of a body shaped like a sourdough loaf, and a romantic frill running along its length.

It has an enormous brain, which resembles a doughnut.

The pupils in its outsized, expressive eyes are shaped like a W; it is colour blind, sadly, but the eyes are among the most developed in the animal kingdom, which is reassuring given the sorts of things it will witness during mating season, which I shall outline shortly.

And yes - it has three hearts. They pump the cuttlefish's blood, which is blue, thus establishing a prima facie case to recommend the creature for an Abbott knighthood (although realistically there would be strong protest from Cory Bernardi, owing to its sexual habits).

Of all the strange attributes of the giant cuttlefish, its skin is the most magical.

It is smooth, but laced with tiny muscles that allow it to become knobbly.

The cuttlefish is known as the ''Chameleon of the Sea'', because it can change colour at will; moody mottled brown, iridescent blue, pale green, sudden stripes.

When especially excited, patterns will actually appear to flow along its flanks; a magical glowing ripple effect, like a 1950s TV, slightly off-station, in a shop window at night.

''Man is the only creature that blushes. Or needs to,'' said Mark Twain, but one imagines he had not encountered the giant cuttlefish.

Scientists at Harvard announced in January that they had successfully reverse-engineered cuttlefish skin, in the hope of one day building adaptive camouflage gear for humans, which would certainly make life easier for sailors currently obliged to cover themselves in cephalopods for the same effect.

But the most charmingly preposterous thing about the Australian giant cuttlefish is its sex life.

The reason Point Lowly is famous among cuttle-fanciers is that this unassuming little spot is - every winter - the site of an all-in, depraved cuttlefish orgy, a festival of invertebrate concupiscence unchallenged anywhere else in the world.

Males outnumber females by about eight to one, and are thus obliged to put on incredible psychedelic displays; pulsating zebra stripes, patterns, wild flashes of colour; it's like watching a hundred thousand iPads trying to have sex.

The big ones tend to win out, so the smaller males do something quite unusual; they switch from gaudy ''male'' colours to more muted female ones, and - while thus cross-dressed - slip into the fray hoping for a sly shag.

The giant cuttlefish lives for only two years, and after this winter Mardi Gras, it will slink off and die, ideally to become a calcium supplement for the Giant Budgie.

But the mystery of Point Lowly is this: in recent years, the cuttlefish have disappeared.

From the erotic heights of 1999, when nearly 200,000 of them gathered for a frenzied bout of ''squid pro quo'', numbers have fallen by 90 per cent and now barely 13,000 rock up.

This year, with winter approaching, locals and tourism operators hope for the best, but fear the worst.

The Spencer Gulf population is regarded by some scientists as a unique cuttlefish species. Where has it gone?

And is it gone for ever?

The creature and its eggs are microscopically sensitive to changes in salinity. And to noise.

And their kinky party-pad is surrounded by shipping lanes, aquaculture projects, the Port Bonython hydrocarbon processing plant and a proposed desalination plant for BHP Billiton.

The specific cause remains a mystery, but the evidence suggests that one of the world's great marine spectacles is soon to be a memory.

The ocean is full of unanswered questions.

Twitter: @annabelcrabb